Automatic installation for liquid chromatography

Abstract

In the automatic installation for liquid chromatography according to the invention, the container of product to be fractionated is associated to a measuring container and is provided, as are the containers of eluents, with low level detector means; feed valves are interposed between said containers and the injection pump whereas output valves are interposed between the outlet from the column and the collector containers; a control unit comprises a safety device connected to the low level detectors to control the stoppage of the pump whenever necessary, and a control device receiving the signals from detection means connected to the output of the column and controlling the measuring container and said valves to perform successive cycles of chromatography each one including the steps of injecting a quantity of product, admitting at least one eluent and collecting the or each corresponding fraction.

What we claim is: 
     
       1. An automatic installation for liquid chromatography, of the type comprising a chromatographic column, a container of the product to be fractionated, and at least one container of eluent, said containers being connectable with the top of the column via an injection pump, detection means connected to the output of the column and supplying at least one measuring signal representing a characteristic of the liquid discharged from the bottom of the column, means for collecting fractions with at least one collector container which is connectable with the base of the column via an automatically-controlled output valve, and a control unit receiving the measuring signal and comprising means for controlling the fractions collecting means, wherein: a level detector is provided for each container of product to be fractionated and of eluent, which detector produces a low level signal whenever the level of the liquid inside the container is below a predetermined threshold,   automatically controlled feed valves are mounted between the injection pump and each container of product to be fractionated and eluent, respectively,   a measuring device is provided for the container of the liquid to be fractionated, to allow injection into the column of a pre-determined quantity of said product, and   the control unit comprises: a control device receiving the or each measuring signal produced by the detection means and controlling on the one hand, the feed and output valves and, on the other hand, the measuring device, to produce successive cycles of chromatography each one including at least the consecutive operations of injecting into the column a set quantity of the product to be fractionated, of admitting in the eluent, and of collecting a fraction; and a safety device connected to the level detectors to control the stoppage of the pump and prevent admission of product to be fractionated or of eluent into the column when the corresponding level detector produces a low-level signal.   
     
     
       2. An installation as claimed in claim 1, wherein the detection device comprises a plurality of detectors producing different measuring signals representing different characteristics of the liquid discharged from the column. 
     
     
       3. An installation as claimed in claim 1, in which the control device is of the type comprising a comparator to initiate the collection of one fraction when a measuring signal produced by the detection means crosses, in one direction, a first preset and adjustable threshold, wherein said control device comprises a second comparator to interrupt the collection of the fraction when the measuring signal crosses in the other direction a second preset threshold adjustable independently of the first. 
     
     
       4. An installation as claimed in claim 1, wherein said control device comprises means of controlling the admission of an eluent into the column and means of detecting the balancing of the column with the admitted eluent, said means responding to at least one measuring signal to control the injection of a quantity of product to be fractionated. 
     
     
       5. An installation as claimed in claim 4, wherein the balance detection means comprise a comparison device receiving said measuring signal and producing an output signal when the amplitude of the measuring signal is within an adjustable predetermined range. 
     
     
       6. An installation as claimed in claim 4, wherein the balance detection means comprise a circuit for eliminating any untimely detection. 
     
     
       7. An installation as claimed in claim 4, wherein said installation comprises a plurality of containers of eluent and the control device receives the measuring signal or signals from the detection device for controlling the successive cycles, each one comprising: the injection of a predetermined quantity of product to be fractionated, the admission of a first eluent into the column, the collection of a first fraction, the admission of a second eluent into the column, the collection of a second fraction, and if necessary, at least one additional sub-cycle comprising the admission of another eluent into the column and the collection of the corresponding fraction, and finally the admission of the first eluent into the column to re-balance it before the start of the next cycle. 
     
     
       8. An installation as claimed in claim 7, wherein the control device comprises means of controlling the admission of eluent acting in response to the end of the injection of the product to be fractionated or to the end of the collection of one fraction. 
     
     
       9. An installation as claimed in claim 1, wherein said installation comprises a plurality of collector containers, each one of which is associated to a single output valve controlled by said control device to connect the container with the column, and to a level detector which is designed to produce a high level signal when the level of the liquid inside the container rises above a predetermined threshold, said detector being connected to the safety device. 
     
     
       10. An installation as claimed in claim 1, wherein the detection means comprise a concentration detector equipped with a tube through which can flow the liquid discharged from the column, a coil wound about said tube, and a measuring circuit to measure the variations of inductance of the coil. 
     
     
       11. An installation as claimed in claim 1, wherein said installation comprises a plurality of chromatographic columns each one with its own control unit, and a collector container associated to one column is combined with measuring means to constitute the container of product to be fractionated feeding another column. 
     
     
       12. An installation as claimed in claim 1, wherein said measuring means consist of a container provided with two probes placed at different levels, which container is connectable, on the one hand, with the container of product to be fractionated via a first valve, and on the other hand, with the column via a second valve, and the control device comprises a circuit receiving the signals of the two level probes associated to the measuring device and a control signal, said control device controlling the valves in order to introduced into the measuring container or extract therefrom a quantity of liquid corresponding to the level differences between the two probes.